“Empyrean” comes from the Greek word “empurios,” from “en” (“in”) and “pur” (“fire”). It can be used as a noun and a verb, both relating to the heavens and the sky. The noun “empyrean” specifically denotes the highest part of the heavens — in medieval times, the highest heavens were believed to possess their own fire, which is likely how the word “empyrean” developed. The adjective “empyrean” describes anything relating to the sky or the heavens. You can use this word to describe stars, clouds, planets, rockets, and outer space exploration.